   ([] (typical-stage-length (rand-length-unit)))
   ([length-unit]
    (condp = length-unit
-     :ft [(tuc/draw-normal 152 17) :ft]
-     :m [((convert-units-f :ft :m) (nth (typical-stage-length :ft) 0)) :m])))
+     :ft (make-measurement (tuc/draw-normal 152 17) :ft)
+     :m (length-as (typical-stage-length :ft) :m))))
 
 (defn typical-stage-extent
   ([]

        measurement (generate-measurement-f unit)]
    [measurement (measurement-as-f measurement (first (remove (partial = unit) units)))]))

(generate-measurement-pair (set (quantity-unit-map :density))
                           rand-density-unit typical-density density-as)

(defn rand-measurement
  ([]

((quantity-generate-measurement-map :duration))
((quantity-generate-measurement-map :duration) (rand-unit :duration))
(rand-measurement :duration)
